Up to now, WAVE (wireless access in vehicular environments) has been known as a communication standard for performing a wireless communication between a communication device (hereinafter referred to as “service provision device”) managed by a service provider that provides a predetermined service and a communication device (hereinafter referred to as “vehicle side device”) used in a vehicle (for example, Patent Literature 1).
In the WAVE, the service provision device and the vehicle side device perform the wireless communication with the use of two types of communication channels including a control channel (hereinafter referred to as CCH: control channel) and a service channel (hereinafter referred to as SCH: service channel). The SCH is a communication channel used for transmitting and receiving information for performing the provision and use of services. Multiple frequencies used as the SCH are prepared. In other words, multiple communication channels are prepared as service channels.
In addition, the CCH is a communication channel used for distributing a message (WSA: wave service advertisement) for initiating a communication between the vehicle side device and the service provision device with the use of the SCH, and so on. The WSA includes service type information indicating the type of services provided by the service provision device as a source of the WSA and channel information designating the SCH used for providing the service among the multiple SCHs.
The vehicle side device receives the WSA transmitted from the service provision device with the use of the CCH to grasp currently available services. The vehicle side device performs a communication with the service provision device that provides a service to be used with the use of the SCH indicated in the WSA corresponding to the service, to thereby use the service. The type of service to be used is registered in advance in the vehicle side device.
In addition, each communication device in the WAVE is set so as to implement a communication using the CCH and a communication using the SCH alternately at predetermined time intervals (for example, 50 milliseconds) as a basic communication pattern (which is taken as a standard method). Therefore, when using the service corresponding to the WSA received while carrying out the communication by the CCH, the vehicle side device starts the communication using the SCH indicated in the WSA at the time point when the communication using the CCH is ended after an elapse of a predetermined communication period.
For the sake of convenience, in the following description, the time period during which the communication using the control channel is scheduled to be carried out in the standard method is referred to as a CCH time period, and the time period during which the communication using the service channel is scheduled to be carried out is referred to as an SCH time period.
In the WAVE, various communication patterns other than the standard method described above are prepared as the communication patterns between the service provision device and the vehicle side device. For example, as the communication pattern other than the standard method, there is an immediate start method of starting the communication using the SCH shown in the WSA immediately upon receiving the WSA. Upon receiving the WSA for which the immediate start method is designated, the vehicle side device promptly terminates the communication by the CCH and starts the communication using the SCH indicated in the received WSA.
In the WSA, an area (hereinafter referred to as option area) for designating the communication pattern is provided, and the service provision device designates a desired communication pattern in the option area of the WSA so as to be communicatable with the vehicle side device by the designated communication pattern.